1. Field of the Invention
The present invention relates to a droplet jet head that ejects droplets, and to a droplet jet applicator having the droplet jet head.
2. Description of the Related Art
A droplet jet head is a droplet jet unit (for example, an inkjet head) that ejects liquid including ink as a droplet from each of a plurality of nozzles, aiming the liquid at an application target. A droplet jet applicator having the droplet jet head is generally used for manufacturing various display devices such as a liquid crystal display device, an organic electroluminescence (EL) display device, an electron emission display device, a plasma display device and an electrophoretic display device. This droplet jet applicator causes droplets to land on a substrate being an application target by use of the droplet jet head, thus forming a dot line with a predetermined pattern. Consequently, the droplet jet applicator manufactures a coated body, for example, a color filter and a black matrix (a frame of a color filter).
Such a droplet jet head includes a base member, a vibration plate, a liquid chamber plate and a nozzle plate. The base member holds a plurality of piezoelectric elements. The vibration plate is provided on the base member and is vibrated by each piezoelectric element. The liquid chamber plate is provided on the vibration plate and has liquid chambers containing liquid. The nozzle plate is provided on the liquid chamber plate and has a plurality of nozzles communicating with the liquid chambers, respectively (refer to JP-A No. 2005-270743 (KOKAI), for example). The nozzle plate is formed of a material such as glass. The base member, the vibration plate, the liquid chamber plate and the nozzle plate are fastened by a plurality of screws each of which penetrates through the base member and these plates. The stronger the fastening force is, the more stable the jet performance of the droplet jet head becomes.
However, if the fastening force of screwing is too strong, a crack appears in the nozzle plate, since the nozzle plate is formed of a material such as glass, and also the screws press the nozzle plate directly. For this reason, the fastening force of screwing is set to have a strength in such a degree that the nozzle plate is not to be damaged. Thus, energy from the piezoelectric elements is not conveyed to the nozzle efficiently. This makes the jet performance unstable, and thereby landing accuracy of droplets lower.